KR20030029485A - Display driving apparatus and driving control method - Google Patents

Abstract

PURPOSE: To provide a liquid crystal driving device in which adverse effect caused by a change ΔΔV in a field-through voltage ΔV of liquid crystal pixels due to an applied voltage is reduced, the occurrence of flicker and burning is suppressed, high quality display is realized, deterioration of liquid crystal elements is suppressed and the reliability of the liquid crystals is improved. CONSTITUTION: Whenever a common electrode potential is reversed, a voltage corresponding to a control value based on contrast setting signals CTA and CTB and a correction voltage setting signal DV is selected from among the voltages of a plurality of steps generated by a γ reference voltage generating section 11 by MXVA 121 and MXVB 123 of a reference voltage selecting section 12 and the voltage is outputted as a highest/a lowest gradation reference voltage. Among the center voltage of the highest/lowest gradation reference voltages being outputted every time the common electrode potential is reversed, the center voltage of one of the gradation reference voltages, that make the voltage to be applied to the liquid crystal pixels become low, is set higher with respect to the center voltage of the other gradation reference voltage equivalent to a voltage corresponding to the signal DV. The voltage corresponding to the signal DV is set to a difference ΔΔV of the voltage ΔV when one of the gradation reference voltages is applied to the liquid crystal pixels and the other gradation voltage is applied.

Description

DISPLAY DRIVING APPARATUS AND DRIVING CONTROL METHOD}

The present invention relates to a display driver for driving a liquid crystal display panel and a display device using the same, and more particularly to a display driver for driving an active matrix liquid crystal display panel.

Background Art [0002] In recent years, display apparatuses using liquid crystal display panels for displaying images and text information have been widely used in image pickup devices, mobile phones, portable information terminals (PDAs), and the like, which are widely used in digital video cameras and digital still cameras. In addition, as a monitor or a display of an information terminal such as a computer or a video device, a display device using a liquid crystal display panel has been used in place of a conventional CRT.

As liquid crystal display panels used for such applications, active matrix type liquid crystal display panels (hereinafter referred to as TFT-LCDs) using thin film transistors (TFT) as switching elements, which have relatively high image quality, have been used.

Below, the main part structure of the conventional display apparatus using TFT-LCD is demonstrated with reference to drawings.

The TFT-LCD is a display in which a TFT and a liquid crystal display pixel for selectively applying voltage to each liquid crystal display pixel are arranged in a matrix on a glass substrate.

11 shows an equivalent circuit of the liquid crystal display pixel 100 in the TFT-LCD. As shown in the same figure, the liquid crystal display pixel 100 is provided at the intersection of the gate line GL extending in the row direction and the data line DL extending in the column direction, and the gate electrode G is connected to the gate line GL. Is connected to the data electrode DL, the pixel electrode connected to the drain electrode D of the TFT, and the counter electrode 1 opposite to the pixel electrode. the liquid crystal display comprises a pixel capacitance (C _LC) and a storage capacitor composed of a dielectric film sandwiched between the pixel electrode and the storage capacitor electrode (2) (C _S) composed of a liquid crystal. In the TFT-LCD, the liquid crystal display pixels 100 are arranged in a plurality of matrix forms. The common electrode VCOM is commonly connected to the counter electrode 1 and the storage capacitor electrode 2 of each liquid crystal display pixel 100.

12A to 12D show an example of a timing chart of signal waveforms driving the TFT-LCD.

V _G in Fig. 12A is a waveform diagram showing the potential of the gate line (GL), a scanning signal. In addition V _S of Figure 12B is a waveform diagram showing the potential of the data line (DL), and a voltage corresponding to the display data signal, and the center voltage V _S to the DC. These signals of V _G and V _S are applied to the gate electrode G and the source electrode _S of the TFT, respectively.

And V _COM in Figure 12C is a waveform diagram showing the potential of the opposing electrode (1) and the storage capacitor electrode (2) connected to the common electrode (VCOM), a central voltage V _COM to DC.

In addition, since deterioration occurs when a direct current voltage is applied to the liquid crystal, V _S and V _COM are inverted in polarity, for example, in each frame.

FIG. 12D illustrates a change in the voltage V _LC applied to the liquid crystal capacitor C _LC of the liquid crystal display pixel 100.

As shown in the same drawing, when the potential of the gate line GL is at the "Hi" level at the time T1 of the first frame, and the TFT is turned "ON", the potential of the pixel electrode is lower than that of the data line DL. Becomes equal to the potential V _S. Accordingly, the voltage of the difference between the potential applied to the common electrode VCOM and the potential V _S of the data line DL is applied to the liquid crystal capacitor C _LC .

At time T2, the potential of the gate line GL is at the "Low" level, and the TFT is turned to the "OFF" state. Accordingly, the charge applied to the liquid crystal capacitor C _LC is maintained at the time T1, and the potential change at the instant when the potential of the gate line GL becomes the "Low" level is the gate-drain parasitic capacitance of the TFT ( The voltage V _LC applied to the liquid crystal capacitor C _LC decreases by the field-through voltage ΔV to be described later, which acts in the direction of lowering the potential of the pixel electrode through C _GD ).

In the second frame, the potential V _S of the data line DL and the potential V _COM of the common electrode VCOM are inverted, and at this time T3, the potential of the gate line GL is at the "Hi" level. As a result, when the TFT is turned “ON”, the potential of the pixel electrode is equal to the potential V _S of the data line DL, and the voltage and the data line applied to the common electrode VCOM are applied to the liquid crystal capacitor C _LC . The voltage of the difference of the potential V _S of DL is applied.

At the time T4, the potential of the gate line GL becomes the "Low" level, similarly to the time T2, so that the TFT is in the "OFF" state, and thus is applied to the liquid crystal capacitor C _LC at the time T3. The charged charge is maintained, and the change in potential at the moment when the potential of the gate line GL reaches the "Low" level is influenced through the gate-drain parasitic capacitance C _GD of the TFT and applied to the liquid crystal capacitor C _LC . The voltage V _{LC to} be lowered by the field-through voltage ΔV. After that, the TFT is turned “OFF” to maintain the charge applied to the liquid crystal capacitor C _LC .

This field through voltage (ΔV) is

ΔV = ΔV _G × (C _GD / (C _GD + C _LC + C _S )) ········· (1)

It is represented by

ΔV _G is the amount of change in the potential of the gate line, C _GD is the gate-drain parasitic capacitance, C _LC is the liquid crystal capacitance of the pixel electrode portion, and C _S is the auxiliary capacitance.

As shown in FIG. 12D, the variation of the field-through voltage ΔV occurs in the voltage V _LC applied to the liquid crystal capacitor C _LC , so that the waveform of V _LC becomes a waveform having a positive and negative asymmetry with respect to V _COM . The difference in the amount of positive and negative charge held in the liquid crystal capacitor C _LC causes a DC voltage component.

As a result, flickering occurs and at the same time, direct current voltage is applied to the liquid crystal, causing seizing to deteriorate the display quality.

In addition, when a direct current voltage is applied to the liquid crystal, the liquid crystal is deteriorated, and the reliability of the liquid crystal is lowered.

In order to solve the above problem, conventionally, for example, the center voltage V _S DC of the potential V _S of the data line DL is set to be about ΔV high, and the voltage is applied to the liquid crystal capacitor C _LC . By adjusting the amount of positive and negative charges held in the liquid crystal capacitor C _LC by V _LC to be approximately equal, the DC voltage component is reduced to suppress the occurrence of flicker, while suppressing the occurrence of sticking and deterioration of the liquid crystal. I was trying to.

However, the liquid crystal capacitor C _LC is not constant with respect to the voltage V _LC applied to the liquid crystal. 13 shows an example of the change characteristic of the relative dielectric constant? _R of the liquid crystal with respect to the applied voltage V _LC . As shown in the same figure, the relative dielectric constant epsilon _r of the liquid crystal generally has a characteristic of increasing as the applied voltage V _LC increases.

Here, the liquid crystal capacitance C _LC is

C _LC = ε _O ^＊ ε _r ^＊ S / d

It is the liquid crystal capacitor (C _LC) value is also changed, and increases with the applied voltage (V _LC) becomes larger depending on the applied voltage (V _LC) because of. Where “S” is the pixel electrode area, “d” is the cell gap, and ε _O ^＊ is the dielectric constant of vacuum.

Voltage to be applied here to the liquid crystal (V _LC) is a voltage based on the voltage (V _S) of the data line (DL), the data line (DL) potential (V _S) is because a voltage corresponding to the display data signals It is not constant but changes in accordance with the display data signal.

That is, since the liquid crystal capacitor C _LC changes in accordance with the applied voltage V _LC , the field-through voltage ΔV also changes in accordance with the applied voltage V _LC according to the equation (1). Here, the amount of change in ΔV due to the applied voltage V _LC is ΔΔV.

For this reason, the applied voltage V _LC adjusts the center voltage V _S DC of the data line DL in response to a state of a certain value (for example, the maximum voltage), and in that state, the voltage V _LC is adjusted by the voltage V _LC . Even if the amount of positive and negative charges held in the liquid crystal capacitor C _LC is adjusted to be approximately equal, the applied voltage V _LC is a voltage corresponding to the display data signal and is always changing as described above. Thus, accordingly the field through voltage (△ V) also changes will because of the applied voltage (V _LC) discard to the amount of charge of the positive and negative changes to be held in the liquid crystal capacitor (C _LC) If the change to the liquid crystal capacitor (C _LC) It could not be adjusted so that the amount of positive and negative charges maintained was always the same.

Therefore, in the related art, it has been practiced to make the storage capacitor C _LC relatively small by reducing the storage capacitance C _S so that the influence of the change in the liquid crystal capacitance C _LC is reduced. .

However, in order to increase the storage capacitor (C _S) designed without increasing the area of the electrode to form a C _S, thus the aperture ratio is lowered to discard it. As a result, display quality deteriorates or the brightness of the backlight must be increased, resulting in increased power consumption.

In recent years, in order to reduce the number of devices driven by battery driving and to reduce power consumption, the use of low-voltage liquid crystals that operate at lower voltages in response to lower driving voltages has increased. In this case, since the liquid crystal capacitance decreases due to the decrease in the liquid crystal applied voltage, the field through voltage DELTA V tends to increase. For this reason, there is a problem that the influence of the change of the field through voltage DELTA V according to the applied voltage V _LC increases, the flicker, the lagging, etc. increase, and the deterioration of the display quality increases.

The present invention provides a display driving apparatus for driving an active matrix liquid crystal display panel, wherein the display device using the display driving apparatus is corrected by correcting a voltage level applied to the display pixel according to a change in the field through voltage of the display pixel. It has the advantage of suppressing the occurrence of flicker or sticking without increasing the auxiliary capacitance to obtain high quality display and improving the reliability of the liquid crystal.

In order to obtain the above advantages, the display driving device and the display device using the same include a plurality of pixel electrodes arranged in a matrix, a common electrode facing the pixel electrode, and a gap between the pixel electrode and the common electrode. An active matrix liquid crystal display panel comprising a plurality of liquid crystal display pixels composed of liquid crystals, a common electrode inverting means for inverting the potential of the common electrode of the liquid crystal display panel every predetermined period, and a contrast set value and a correction voltage set value. According to the common electrode inverting means, the lowest gradation reference voltage and the highest gradation reference voltage are set whenever the common electrode potential is inverted, and each of the lowest gradation reference voltage and the highest gradation reference voltage when the common electrode potential is inverted. One of the variable center voltages, the voltage at which the voltage applied to the liquid crystal display pixel becomes smaller is corrected for the other And a gradation reference voltage setting means for setting the voltage as high as the voltage corresponding to the set value.

The voltage corresponding to the correction voltage setting value in the gradation reference voltage setting means corresponds to the liquid crystal when one of the lowest gradation reference voltage or the highest gradation reference voltage is applied to the liquid crystal display pixel in the active matrix liquid crystal display panel. It is a voltage value of the difference of the value of the field through voltage in a display pixel, and the value of the field through voltage in the said liquid crystal display pixel when the other voltage is applied.

The gradation reference voltage setting means comprises a contrast set value from the γ reference voltage generating means for generating plural levels of voltage, and the plural steps of voltage generated by the γ reference voltage generating means each time the potential of the common electrode is reversed. The first voltage selecting means for selecting and outputting the first voltage of the step corresponding to the first value based on the correction voltage setting value, and the voltage of the plurality of steps generated from the voltage of the plurality of steps generated by the? Reference voltage generating means. Reference voltage selecting means including second voltage selecting means for selecting and outputting a second voltage in a step corresponding to a value obtained by subtracting a second value based on the contrast setting value and the correction voltage setting signal from the maximum value; The first and second voltages output by the reference voltage selecting means alternately output as the lowest gray reference voltage and the highest gray reference voltage whenever the potential of the common electrode is inverted. Provided with a voltage output means.

In the first voltage selection means and the second voltage selection means, the first and second values based on the contrast setting value and the correction voltage setting value are the values according to the contrast setting value and the corresponding contrast setting value. Either the value obtained by subtracting the value of the correction voltage setting value from the value of the value, or the maximum value of the number of steps in the reference voltage generating means and the value of the corresponding contrast setting value or the corresponding control. One of the values obtained by subtracting the value of the correction voltage set value from the value set by the streak value, and is alternately set each time the common electrode potential is inverted, and the active matrix liquid crystal display panel is normally white or no. The correspondence of the polarity inversion of the common electrode potential of the first and second values is reversed in accordance with either the far black type.

In order to obtain the above advantages, the driving control method of the display driving apparatus according to the present invention inverts the potential of the common electrode of the active matrix liquid crystal display panel every predetermined period, and generates the lowest gradation reference voltage and voltage whenever the common electrode potential is inverted. The highest gradation reference voltage is set based on the contrast setting value and the correction voltage setting value, and the voltage applied to the liquid crystal display pixel among the variation center voltages of each gradation reference voltage whenever the common electrode potential is inverted becomes smaller. The voltage on one side is set to be higher by the voltage corresponding to the correction voltage set value on the other side. The voltage corresponding to the correction voltage set value is the field through in the liquid crystal display pixel when one of the lowest gray scale reference voltage or the highest gray scale reference voltage is applied to the liquid crystal display pixel in the active matrix liquid crystal display panel. It is a voltage value of the difference of the value of the field-through voltage in the said liquid crystal display pixel when the value of a voltage and the other voltage are applied.

The method for setting the lowest gradation reference voltage and the highest gradation reference voltage based on the contrast set value and the correction voltage set value generates a plurality of gray level voltages, and the potential of the common electrode is inverted from the plurality of gray level voltages. Every time the first voltage of the step corresponding to the first value based on the contrast set value and the correction voltage set value, and the maximum value of the number of steps, based on the contrast set value and the correction voltage set value. Select and output the second voltage in the step corresponding to the subtracted value of 2, and set the first voltage and the second voltage as the lowest gray reference voltage and the highest gray reference voltage each time the potential of the common electrode is reversed. do.

Any of the values obtained by subtracting the value of the contrast setting value and the value of the contrast setting value subtracted from the value of the contrast setting value based on the contrast setting value and the correction voltage setting value. Or the value obtained by subtracting the value of the correction voltage set value from the maximum value of the number of steps of the gradation voltage and the corresponding contrast set value, and the number of steps of the value and contrast value of the contrast set value. Either of these maximum values is set alternately each time the common electrode potential is reversed. In addition, depending on whether the driving active matrix liquid crystal display panel is normally white or normally black, the correspondence between the first and second values whenever the common electrode potential is reversed in polarity is set.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a block diagram showing a main part of a display device to which a display drive device according to the present invention is applied.

2 is a block diagram showing the configuration of a gradation reference voltage generation circuit according to the present invention;

FIG. 3 is a circuit diagram showing an example of a specific configuration of a gamma reference voltage generator in a gray reference voltage generation circuit of the present invention. FIG.

4 is a circuit diagram showing an example of a specific configuration of the reference voltage output section 13 in the gradation reference voltage generation circuit of the present invention.

Fig. 5 is a circuit diagram showing main parts of TGA and TGB in the first embodiment of the reference voltage selecting section.

Fig. 6 is a timing chart showing operations of TGA and TGB in the first embodiment of the reference voltage selection unit.

Fig. 7 is a diagram showing the voltage values of the black gradation voltage and the white gradation voltage in comparison with the conventional values in the first embodiment.

8A and 8B are circuit diagrams showing main parts of TGA and TGB in the second embodiment of the reference voltage selection unit.

Fig. 9 is a timing chart showing operations of TGA and TGB in the second embodiment of the reference voltage selecting section.

Fig. 10 is a diagram showing the voltage values of the black gradation voltage and the white gradation voltage in comparison with the conventional values in the second embodiment.

Fig. 11 is an equivalent circuit of a liquid crystal display pixel in TFT-LCD.

12A to 12D are timing charts of signal waveforms for driving a TFT-LCD.

FIG. 13 is a diagram showing an example of a change characteristic with respect to an applied voltage of a dielectric constant of a liquid crystal. FIG.

※ Explanation of symbols for main parts of drawing

11: γ reference voltage generator 12: reference voltage selector

13: Reference voltage output section 121: MXVA

122: TGA123: MXVB

124: TGB200: gradation reference voltage generation circuit

300: source driver 306: liquid crystal display panel

400: gate driver

EMBODIMENT OF THE INVENTION Hereinafter, the detail of the display drive apparatus which concerns on this invention, the display apparatus using the same, and its drive control method is demonstrated in detail based on embodiment shown in drawing.

<1st embodiment>

First, a first embodiment of a display drive device according to the present invention will be described with reference to the drawings.

1 is a block diagram showing a main part of a display device to which the display drive device according to the present invention is applied.

As shown in the same figure, the liquid crystal display device includes a gradation reference voltage generation circuit 200, a source driver 300, a gate driver 400, and a liquid crystal display panel 306. FIG.

The liquid crystal display panel 306 is the same active matrix type TFT-LCD as in the prior art, but is not shown in detail, but a plurality of gate lines GL stretched in a row direction and a plurality of data lines DL stretched in a column direction. And the same liquid crystal display pixel as the liquid crystal display pixel 100 shown in FIG. 9 at each intersection of the gate line GL and the data line DL.

The source driver 300 includes a shift register 301, a data register 302, a latch circuit 303, a D / A converter 304, and an output buffer 305. The shift register 301 includes a clock signal ( CK and the shift start signal STR are applied, and the applied shift start signal STR is sequentially shifted by the clock signal CK.

The data register 302 is provided with a plurality of register circuits, for example, to which display data D0 to D7 consisting of 8-bit digital data is applied, and at the timing of a control signal supplied from the shift register 301, the display signal. Are sequentially received and output to the latch circuit 303.

The latch circuit 303 includes a plurality of data holding circuits, and when the latch operation control signal STB is applied, display data received by the data register 302 is held in the latch circuit 303, and at the same time, the D / A converter Is output to 304.

The D / A converter 304 receives a gray reference voltage (lowest gray voltage V0, highest gray voltage V8) from the gray reference voltage generation circuit 200, and generates a voltage for each gray level based on this. At the same time, a plurality of D / A conversion circuits are provided, and the display data composed of digital data supplied from the latch circuit 303 is decoded, converted into a gradation voltage value corresponding to the display data value, and output to the output buffer 305. do.

Although the gradation reference voltage generation circuit 200 will be described in detail later, the predetermined voltages Vdd and Vss are supplied and the polarity inversion control signal POL, the correction signal DV, and the contrast setting signal are provided as control signals. (CTA, CTB) are applied, and a gray scale reference voltage is appropriately generated based on these control signals.

The output buffer 305 is supplied with the display data signal converted into the gray scale voltage by the D / A converter 304, the enable signal OE is applied, and each data line DL of the liquid crystal display panel 306. Supplied to.

Although not shown in detail, the gate driver 400 includes a shift register and an output buffer circuit, and a gate clock signal GCK and a gate start signal GST are applied, and the gate start signal GST is a gate clock signal. The shift operation is performed in sequence by GCK, and the scan signal generated accordingly is supplied to each gate line GL of the liquid crystal display panel 306 in sequence. As a result, the TFTs connected to the respective gate lines are turned ON in turn, and the display data signals supplied to the data lines DL from the output buffer 305 of the source driver 300 are supplied to the liquid crystal display pixels to perform image display operation. This is carried out.

In addition, various control signals applied to the source driver 300 and the gate driver 400 are supplied from a controller circuit (not shown).

In the present embodiment, however, in the configuration of the liquid crystal display device, the reference voltage at the time of determining the gradation voltage corresponding to the gradation of the display data signal supplied to each data line DL of the liquid crystal display panel 306 is used. It is characterized by the method of setting the gradation reference voltage supplied to the D / A converter 304, and in particular, the structure of the gradation reference voltage generation circuit 200 related to the setting of the gradation reference voltage.

2 is a block diagram showing the configuration of the gray scale reference voltage generation circuit 200 according to the present invention.

As shown in the same figure, the gradation reference voltage generation circuit 200 is constituted by the γ reference voltage generation section 11, the reference voltage selection section 12, and the reference voltage output section 13.

The gamma reference voltage generator 11 is supplied with a predetermined voltage (Vdd, Vss) (Vdd is a power supply voltage on the high voltage side, and Vss is a power supply voltage on the low voltage side) from the outside, and the voltage (Vdd-Vss) is an example. For example, it divides into 256 steps, generates the reference voltage of 256 steps which consists of Vc (0)-Vc (255), and outputs it to the reference voltage selection part 12. FIG.

3 shows an example of a specific circuit configuration of the gamma reference voltage generator 11. That is, as shown in the same drawing, the γ reference voltage generator 11 has a plurality of resistors Rdn and Rc connected in series between the supplied voltages Vdd and Vss, thereby dividing the voltage between Vss and Vdd. It is configured to generate and output one voltage (Vc0 to Vc255).

The reference voltage selector 12 includes a first voltage selector by the MXVA 121, a TGA 122, and a second voltage selector by the MXVB 123 and the TGB 124. The MXVA 121 and the MXVB 123 are reference voltages Vc (0) to Vc (255) supplied from the gamma reference voltage generator 11 according to control values input from the TGA 122 and the TGB 124, respectively. Select the corresponding voltage from).

CTA [7: 0], DV [7: 0] and POL are input to the TGA 122 as control signals, and CTB [7: 0], DV [7: 0] and POL are input to the TGB 124. .

Here, CTA [7: 0] and CTB [7: 0] (hereinafter referred to as "CTA" and "CTB") are contrast setting signals for setting the contrast value of the display image. It consists of [7: 0] which shows 8 bits. In addition, it is not limited to 8 bits, It goes without saying that the number of other bits may be sufficient.

DV [7: 0] is a correction signal for setting the liquid crystal display mode and the DELTA V correction voltage value. The DV [7: 0] is composed of 8 bits in the same manner and is represented in the form of [7: 0]. This is not limited to 8 bits, of course, but may be any other number of bits.

Here, DV [7], which is the most significant bit of DV [7: 0], is used to indicate the liquid crystal display mode as follows. That is, the liquid crystal display mode includes a normally white method (hereinafter referred to as "NW method") and a normally black method (hereinafter referred to as "NB method"), and is set according to the type of arrangement of the polarizing plate. The NW method is a display method in which a liquid crystal device has a white display when no voltage is applied, and when the voltage is applied, the transmittance decreases and becomes a black display. The NB method is the reverse. Corresponding to each, DV [7] is set to "0" in the case of the NW system and DV [7} is set to "1" in the case of the NB method.

Subsequently, 7-bit DV [6: 0] except the most significant bit is used as the? V correction voltage setting signal as follows. That is, DV [6: 0] is a field of the liquid crystal display pixel when the highest gradation reference voltage V8 generated by the gradation reference voltage generation circuit 200 is applied to the liquid crystal display pixel of the liquid crystal display panel 306. Corresponds to the voltage value (ΔΔV) obtained by subtracting the value of the field-through voltage (ΔV) of the liquid crystal display pixel when the lowest gradation reference voltage (V0) is applied to the liquid crystal display pixel from the value of the through voltage (ΔV). It is set to one value.

That is, the MXVA 121 and the MXVB 123 select a voltage of a step corresponding to a control value input from the TGA 122 and the TGB 124 from a plurality of voltages supplied from the γ reference voltage generator 11. The value of DV [6: 0] is set so that the voltage selected according to the value of the correction voltage setting signal by DV [6: 0] becomes a voltage value of ΔΔV. In addition, it mentions later in detail.

POL is a polarity inversion control signal that controls the polarity inversion of the common electrode potential (V _COM ). When POL is "1", V _COM is at the "Hi" level. When POL is "0", V _COM is " Low ”level.

The TGA 122 and the TGB 124 are configured based on the control signals of the contrast setting signals CTA and CTB, the correction signal DV, and the polarity inversion control signal POL. 123) outputs VA and VB as control values for selecting a voltage that becomes a gray scale reference voltage from the voltages of the plurality of stages supplied from the gamma reference voltage generator 11. In addition, it mentions later in detail.

The control values VA and VB are set within the range of the number of gray levels of the reference voltage output from the? Reference voltage generator 11. For example, in Fig. 1, since the number of gray levels of the reference voltage is 256, the control values VA and VB are set in a range of 0 to 255.

The MXVA 121 selects a voltage of a step corresponding to the control value VA from a plurality of levels of reference voltages input from the gamma reference voltage generator 11 in accordance with the control value VA, and outputs it as VpA. . That is, VpA = Vc (VA).

The MXVB 123 corresponds to a value obtained by subtracting the control value VB from the maximum value of the number of steps from the reference voltage of the plurality of steps input from the? Reference low voltage generation unit 11 according to the control value VB. Select the voltage of and output as VpB. In other words, VpB = Vc (255-VB).

The reference voltage output section 13 is composed of a buffer circuit and a plurality of switches, the polarity inversion control signal POL is supplied, and alternately VpA and VpB input from the reference voltage selector 12 whenever POL is inverted. Output as V0 and V8. That is, when POL = 0, VpA is output as V0 and VpB is output as V8. When POL = 1, VpB is output as V0 and VpA is output as V8.

An example of a specific circuit configuration of the reference voltage output section 13 is shown in FIG. That is, as shown in the same drawing, the reference voltage output section 13 includes buffer circuits BFA401 and BFB402 and switches SRA, SRB, SNA and SNB. The switches SNA and SNB are driven by the polarity inversion control signal POL, and the switches SRA and SRB are driven by the inverters 403 and 404 from the polarity inversion control signal POL. Therefore, when POL = 0, the switches SRA and SRB turn ON (conduction), SNA and SNB turn OFF (non-conduction), and output VpA as V0 and VpB as V8, and when POL = 1, switch SRA and SRB ) Is OFF (non-conduction), SNA, SNB is ON (conduction), and outputs VpB as V0 and VpA as V8.

FIG. 5 is a circuit diagram showing main portions of the TGA 122 and the TGB 124 in the reference voltage selection unit 12. As shown in FIG. That is, the TGA 122 and the TGB 124 have an exclusive logical sum 21 and a multiplexer 22. In addition, since the TGA 122 and the TGB 124 have the same circuit configuration, they will be described with the drawings shown in FIG. 5.

As shown in the same drawing, the exclusive logical sum 21 is inputted with the most significant bit DV [7] indicating the liquid crystal display mode in the polarity inversion control signal POL and the correction signal DV [7: 0]. The signal S which is the output of this exclusive logical sum 21 is input to the multiplexer 22 as a selection signal.

In the TGA 122 as the input signal of the multiplexer 22, the difference between the contrast setting signal CTA, the contrast setting signal, and the ΔΔV correction voltage setting signal DV [6: 0] ( CTA-DV [6: 0]) is input, and in the TGB 124, CTB and (CTB-DV [6: 0]) are similarly input.

When the selection signal S is "1", the CTA signal is selected in the TGA 122 and the CTB signal is selected in the TGB 124. When the selection signal S is "0", the CTA signal is selected in the TGA 122 (CTA). -DV [6: 0]), and the signal of (CTB-DV [6: 0]) is selected in the TGB 124.

6 is a timing chart showing the operation of the TGA 122 and the TGB 124 in the reference voltage selector 12. Here, the case of DV [7] = 0, that is, the NW system will be described.

In this case, when POL = 1, the selection signal S becomes "1". As a result, the multiplexer 22 outputs a CTA at the TGA 122 and a CTB at the TGB 124 as VA and VB.

When POL = 0, the selection signal S becomes "0". As a result, the multiplexer 22 outputs (CTA-DV [6: 0]) in the TGA 122 and (CTB-DV [6: 0]) in the TGA 122 as VA and VB.

As a result, the difference between the values of VA and VB of POL = 1 and the values of VA and VB when POL = 0 is DV [6: 0]. Since the value of DV [6: 0] is set to a value corresponding to ΔΔV as described above, the gradation reference voltage range is corrected by a value corresponding to ΔΔV as described below.

Next, this embodiment is described using a formula.

Here, DV [7] = 0, that is, the case of the NW system will be described.

In the TGA 122 and the TGB 124, the control values VA and VB output in accordance with the control signal are shown in FIG.

When POL = 0,

When POL = 1

Are output to the MXVA 121 and the MXVB 123, respectively. Accordingly, VpA and VpB output from the MXVA 121 and the MXVB 123 are

When POL = 0,

When POL = 1

Are output to the reference voltage output section 13, respectively.

Accordingly, in the reference voltage output section 13,

When POL = 0, VpA = V0, VpB = V8,

When POL = 1 VpA = V8, VpB = V0,

It becomes From here,

V0 = lowest gradation reference voltage = black gradation voltage,

V8 = highest gradation reference voltage = white gradation voltage.

therefore,

When POL = 0,

When POL = 1

Are output respectively.

Here, the waveform of In, POL = 0 of the data line at the time (DL) potential (V _S) waveform and a data line (DL) potential (V _S) of the time of POL = 1 of a conventional drive is reversed each other Was established as a relationship. That is, the gradation reference voltage range is constant, and it is set so that the value of reversing the gradation reference voltage when POL = 0 becomes the gradation reference voltage when POL = 1.

The gray scale reference voltages V0 'and V8' when POL = 0 are

The gradation reference voltages V0 ”and V8” when POL = 1 is

And V0 '= V8' and V8 '= V0'.

So, comparing the present invention with the conventional technique, that is, comparing equation (6) with equation (8), equation (7) with equation (9),

When POL = 0,

When POL = 1

In the white gradation voltages V8 of the formulas (10) and (11), it is found that Vc (DV [6: 0]) is added to the conventional gradation voltages V8 'and V8'. Can be.

[Delta] V denotes that when the black gradation voltage V8 is applied to the liquid crystal display pixel from the value of the field through voltage ΔV of the liquid crystal display pixel when the white gradation voltage V8 is applied as described above. Since the value of the field-through voltage ΔV of the liquid crystal display pixel is subtracted, in this embodiment, DV [6: 0] is a value corresponding to ΔΔV, that is, Vc (DV [6: 0]). When the polarity inversion control signal POL is inverted by setting so as to be ΔΔV, the white gradation voltage V8 is set to a value as high as ΔΔV as compared with the prior art. Accordingly, as the gradation of the display data signal is changed from the black side to the white side, the gradation voltage corresponding to the gradation of the display data signal is corrected by the amount corresponding to the change of ΔV. Accordingly, the asymmetry every time the voltage V _LC applied to the liquid crystal capacitor C _LC is inverted is always suppressed without changing the display data signal.

Fig. 7 is a diagram showing the voltage values of the black gradation voltage V0 and the white gradation voltage V8 when POL = 0 and POL = 1, compared with the conventional ones.

As shown in the drawing, when POL = 0, the conventional value of V8 was Vc (255-CTB). In the present embodiment, the value is increased by ΔΔV to Vc (255-CTB + DV [6: 0]). do.

When POL = 1, the conventional value of V8 was Vc (CTA-DV [6: 0]). In the present embodiment, the value of V8 is increased by ΔΔV and Vc (CTA-DV [6: 0] + DV [ 6: 0]).

As a result, the gray scale reference voltage range is always corrected without changing the display data signal, thereby suppressing asymmetry every time the voltage V _LC applied to the liquid crystal capacitor C _LC is inverted. Therefore, the generation of flicker, sticking and the like can be suppressed, high quality display can be realized, and deterioration of the liquid crystal element can be suppressed to improve the reliability of the liquid crystal.

Here, the correction voltage setting signal DV [6: 0] in the present embodiment is a value input from the outside. Therefore, the value of this correction voltage setting signal DV [6: 0] can be appropriately set as necessary. For this reason, for example, even when the liquid crystal material used is changed or when the format of the liquid crystal display panel is changed, a value suitable for each case can be input. Therefore, even when the liquid crystal material is changed or the format of the liquid crystal display panel is changed, the optimum gradation voltage can be set at all times without changing the driving circuit, and the display quality is improved by suppressing the occurrence of flicker or lamination. You can.

In the related art, as described above, the voltage V _LC applied to the liquid crystal capacitor C _LC is affected by the change in the display data signal due to the influence of ΔΔV in which ΔV changes according to the applied voltage V _LC . In order to suppress the difference between the positive and negative charges held in the liquid crystal capacitor C _LC , the auxiliary capacitance C _S is relatively increased and the value of the field through voltage DELTA V itself is reduced. According to the structure of this embodiment, since the gradation reference voltage range is always corrected in accordance with the value of ΔΔV, it is not necessary to reduce the value of the field through voltage ΔV as in the prior art. Therefore, it is not necessary to increase the auxiliary capacitance C _S as in the prior art. In other words, the size of the storage capacitor C _S may be as small as necessary to maintain the driving voltage, and can be made smaller than before. Therefore, aperture ratio can be made larger than before, and display quality can be improved. In addition, the brightness of the backlight can be reduced by increasing the aperture ratio, and the effect of reducing power consumption can be obtained.

In addition, although the case of the NW system was described as DV [7] = 0, the present invention is not limited to this, and may be applied to the NB system as DV [7] = 1. In that case, the correspondence of VA and VB to the inversion control signal POL is reversed. Accordingly, the black gradation voltage V0 is corrected in accordance with ΔΔV in the same manner as described above to suppress the occurrence of flicker or streaking, thereby realizing high quality display, and suppressing deterioration of the liquid crystal element. The reliability of the liquid crystal can be improved.

<2nd embodiment>

Next, a second embodiment of the display drive apparatus according to the present invention will be described with reference to the drawings. In the second embodiment, the amplitude (dynamic range) of the voltage supplied to the data line DL is increased in accordance with the display data signal in the first embodiment.

Since the voltage V _LC applied to the liquid crystal capacitor C _LC is the voltage of the difference between the potential V _COM applied to the common electrode VCOM and the potential V _S of the data line DL, the liquid crystal capacitor C LC. _{When the} same voltage V _LC is applied to _LC ) According to the second embodiment, the voltage applied to the common electrode VCOM by the corresponding amount is increased by increasing the amplitude of the potential V _S of the data line DL. The amplitude of (V _COM ) can be reduced. Here, the counter electrode is connected to the common electrode VCOM, and since a relatively large capacity of all the pixels is a load, driving of this requires a great power.

Therefore, according to the second embodiment, since the amplitude of the voltage V _COM applied to the common electrode VCOM can be reduced, the power required for driving the common electrode VCOM can be reduced, and thus the display can be reduced. The power consumption of the drive device can be greatly reduced.

Hereinafter, the structure of this embodiment is demonstrated.

Since the structure of the display apparatus to which the display drive apparatus which concerns on this embodiment is applied is the same as that of FIG. 1 mentioned above as a block diagram, description is abbreviate | omitted.

Here, the present embodiment has a difference in the method of setting the gradation reference voltage in the configuration of the gradation reference voltage generation circuit 200 from the first embodiment, and the TGA in the gradation reference voltage generation circuit 200. (122), the configuration of the TGB 124 is different.

The circuit configuration and operation of the TGA 122 and the TGB 124 in the present embodiment will be described below.

8A corresponds to TGA 122 and FIG. 8B corresponds to TGB 124. That is, the TGA 122 includes the multiplexers 51 and 52, and the TGB 124 includes the multiplexers 53 and 54.

As shown in Fig. 8A, in the TGA 122, the multiplexer 51 includes a contrast setting signal CTA, a contrast setting signal CTA, and a ΔΔV correction voltage setting signal DV [6: 0. ] (CTA-DV [6: 0]) is input, while the most significant bit (DV [7]) indicating the liquid crystal display mode in the correction signal DV [7: 0] is input as the selection signal. do. According to the level of DV [7], either one of CTA or (CTA-DV [6: 0]) is selected and output as the signal SA.

In the same manner as described above, DV [7] is set to “0” in the case of the normally white type (NW system) and DV [7] is set to “1” in the case of the normally black method (NB mode). .

Therefore, as signal SA, (CTA-DV [6: 0]) is output when DV [7] = 0, that is, the NW method, and CTA is output when DV [7] = 1, that is, the NB method. .

Subsequently, the signal SA and the hexadecimal number “FF” 255 are input to the multiplexer 52, and the polarity inversion control signal POL of the common electrode potential V _COM is input as a selection signal. One of the signals SA or hexadecimal &quot; FF &quot; is selected according to the level of and is output as the signal SA.

That is, the signal SA is output as VpA when POL = 0, that is, when the NW method is used, and the hexadecimal number ("FF") is output as VA when POL = 1, that is, when the NB method is used.

8B, in the TGB, the multiplexer 53 includes a contrast setting signal CTB, a contrast setting signal CTB, and a DELTA V correction voltage setting signal DV [6: 0]. Difference (CTB-DV [6: 0]) is input, and DV [7] indicating the liquid crystal display mode is input as the selection signal. The signal of either CTB or (CTB-DV [6: 0]) is output as the signal SB in accordance with the level of DV [7].

That is, when the signal SB is DV [7] = 0, that is, when the NW method is outputted, the CTB is output, and when the DV [7] = 1, that is, when the NB method is used (CTB-DV [6: 0]) Is output.

Subsequently, a hexadecimal number (“FF” 255) and the signal SB are input to the multiplexer 54, and a polarity inversion control signal POL is input as a selection signal. FF ”) or one of the signals SB is output as the control value VB.

That is, when POL = 0, that is, when the NW method, the hexadecimal number ("FF") is output as VB, and when POL = 1, that is, when the NB method, the signal SB is output as VB.

9 is a timing chart showing the operation of the circuits of the TGA 122 and the TGB 124 in the present embodiment. Here, DV [7] = 0, that is, the case of the NW system will be described.

In this case, the control value VA output from the TGA 122 becomes CTA and the control value VB output from the TGB 124 is hexadecimal (“FF”) when POL = 1. do.

When POL = 0, the control value VA output from the TGA 122 is hexadecimal ("FF"), and the control value VB output from the TGB 124 is (CTB-DV [6: 0). ]).

Next, the case where the circuits of the TGA 122 and the TGB 124 of FIGS. 8A and 8B are applied to the reference voltage selector 12 of FIG. 2 will be described using equations.

Here, DV [7] = 0, that is, the case of the NW system will be described.

The gray scale voltages V0 and V8 output from the reference voltage output section 13 are

When POL = 0,

When POL = 1

Becomes

From this, the white gradation voltage V8 at the time of POL = 0 and POL = 1 is the same as in the case of the first embodiment. Therefore, this value is the value which corrected (triangle | delta) V as mentioned above, and the effect similar to 1st Embodiment can be acquired.

On the other hand, the black gradation voltage V0 becomes Vc (255) (maximum value) when POL = 0, that is, in the NW method, and becomes Vc (0) (minimum value) when POL = 1, that is, in the NB method. .

FIG. 10 is a diagram showing the voltage values of the black gradation voltage V0 and the white gradation voltage V8 when POL = 0 and POL = 1 in comparison with the conventional values.

As shown in the same figure, when POL = 0, the value of the conventional black gradation voltage V0 is Vc (CTA-DV [6: 0]), whereas in this embodiment, it is Vc (255).

When POL = 1, the value of the conventional black gradation voltage V0 is Vc (255-CTB). In this embodiment, the value of the black gradation voltage V0 is Vc (0).

I.e., the greater the amplitude of the voltage (V _S) applied to the gray-scale voltage range is to be set larger, and accordingly the data line (DL) with respect to the prior art.

Accordingly, when the voltage V _LC applied to the liquid crystal capacitor C _LC is the same as in the related art, the amplitude of the potential V _COM applied to the common electrode VCOM can be reduced. The amplitude reduction amount of the potential V _COM applied to the common electrode VCOM becomes a value proportional to the amplitude increase amount of V0. As a result, since the voltage amplitude of the potential V _COM can be reduced, power consumption required for driving the common electrode VCOM can be reduced, and power consumption of the display driver can be greatly reduced.

Claims (17)

A display driving device for driving an active matrix liquid crystal display panel having a plurality of liquid crystal display pixels, Common electrode inverting means for inverting the potential of the common electrode of the active matrix liquid crystal display panel every predetermined period; When the common electrode potential is inverted by the common electrode inverting means based on the contrast set value and the correction voltage set value, the lowest gray reference voltage and the highest gray reference voltage are set, and the common electrode potential is inverted. The voltage corresponding to the correction voltage set value with respect to the other of the voltage applied to the liquid crystal display pixel of one of the lowest gradation reference voltage and each of the fluctuation center voltages of the highest gradation reference voltage for each other is smaller. And a gradation reference voltage setting means which is set to be as high as possible. The method of claim 1, The voltage corresponding to the correction voltage setting value in the gradation reference voltage setting means is The voltage which is different from the value of the field-through voltage in the liquid crystal display pixel when one of the lowest gradation reference voltage or the highest gradation reference voltage is applied to the liquid crystal display pixel in the active matrix liquid crystal display panel. And a voltage value of a difference of the value of the field-through voltage in the liquid crystal display pixel when it is applied. The method of claim 1, The gradation reference voltage setting means includes: Γ reference voltage generating means for generating a plurality of voltages; A step corresponding to a first value based on the contrast set value and the correction voltage set value from the plurality of steps of voltage generated by the? Reference voltage generating means each time the potential of the common electrode is inverted; First voltage selecting means for selecting and outputting one voltage; A second based on the contrast setting value and the correction voltage setting signal from the voltage of the plurality of steps generated by the gamma reference voltage generating means each time the potential of the common electrode is inverted, from the maximum value of the number of steps; Reference voltage selecting means including second voltage selecting means for selecting and outputting a second voltage in a step corresponding to a value obtained by subtracting the value; And a reference voltage output means for outputting the first voltage and the second voltage output by the reference voltage selecting means alternately as the lowest gray reference voltage and the highest gray reference voltage whenever the potential of the common electrode is inverted. Display drive device characterized in that. The method of claim 3, wherein The first and second values based on the contrast setting value and the correction voltage setting value in the first voltage selecting means and the second voltage selecting means of the reference voltage selecting means are corresponding contrast setting. One of the value obtained by subtracting the value of the correction voltage setting value from the value of the value and the value of the contrast setting value. And the display driving device is alternately set whenever the common electrode potential is inverted. The method of claim 3, wherein The first and second values based on the contrast setting value and the correction voltage setting value in the first voltage selecting means and the second voltage selecting means of the reference voltage selecting means are: The value obtained by subtracting the value of the correction voltage setting value from the maximum value of the number of steps in the gamma reference voltage generating means and the value of the contrast setting value, the value of the contrast setting value, and the gamma One of the maximum value of the number of steps in the reference voltage generating means, And the display driving device is alternately set whenever the common electrode potential is inverted. An active matrix liquid crystal display panel comprising a plurality of liquid crystal display pixels comprising a plurality of pixel electrodes arranged in a matrix, a common electrode facing the pixel electrode, and a liquid crystal sandwiched between the pixel electrode and the common electrode; Common electrode inverting means for inverting the potential of the common electrode of the active matrix liquid crystal display panel every predetermined period; When the common electrode potential is inverted by the common electrode inverting means based on the contrast set value and the correction voltage set value, the lowest gray reference voltage and the highest gray reference voltage are set, and the common electrode potential is inverted. The voltage corresponding to the correction voltage set value with respect to the other of the voltage applied to the liquid crystal display pixel of one of the lowest gradation reference voltage and each of the fluctuation center voltages of the highest gradation reference voltage for each other is smaller. And a gradation reference voltage setting means which is set to be as high as possible. The method of claim 6, The voltage corresponding to the correction voltage setting value in the gradation reference voltage setting means is The liquid crystal when the voltage of the field through voltage in the liquid crystal display pixel is applied to the liquid crystal display pixel when the voltage of either the lowest gray reference voltage or the highest gray reference voltage is applied to the liquid crystal display pixel. A display device characterized by being a voltage value of the difference of the value of the field-through voltage in a display pixel. The method of claim 6, The gradation reference voltage setting means includes: Γ reference voltage generating means for generating a plurality of voltages; A step corresponding to a first value based on the contrast set value and the correction voltage set value from the plurality of steps of voltage generated by the? Reference voltage generating means each time the potential of the common electrode is inverted; First voltage selecting means for selecting and outputting one voltage; A second value based on the contrast set value and the correction voltage set value from the voltage of the plurality of steps generated by the gamma reference voltage generating means each time the potential of the common electrode is inverted; Reference voltage selecting means including second voltage selecting means for selecting and outputting a second voltage in a step corresponding to a value obtained by subtracting the value; And a reference voltage output means for outputting the first voltage and the second voltage output by the reference voltage selecting means alternately as the lowest gray reference voltage and the highest gray reference voltage whenever the potential of the common electrode is inverted. Display device characterized in that. The method of claim 8, The first and second values based on the contrast setting value and the correction voltage setting value in the first voltage selecting means and the second voltage selecting means of the reference voltage selecting means are corresponding contrast setting. It is either the value by the value and the value by subtracting the value by the correction voltage setting value from the value by the contrast setting value, And alternately set each time the common electrode potential is inverted. The method of claim 8, The first and second values based on the contrast setting value and the correction voltage setting value in the first voltage selecting means and the second voltage selecting means of the reference voltage selecting means are: The value obtained by subtracting the value of the correction voltage setting value from the maximum value of the number of steps in the γ reference voltage generating means and the value of the contrast setting value, the value of the contrast setting value, and the γ One of the maximum value of the number of steps in the reference voltage generating means, And alternately set each time the common electrode potential is inverted. The method of claim 8, The reference voltage selecting means, Depending on whether the active matrix liquid crystal display panel is normally white or normally black, Corresponding to the polarity inversion of the common electrode potential of the first and second values based on the contrast set value and the correction voltage set value in the first voltage select means and the second voltage select means. Display device characterized in that the reverse. In the drive control method of a display drive device for driving an active matrix liquid crystal display panel having a plurality of liquid crystal display pixels, The electric potential of the common electrode of the active matrix liquid crystal display panel is inverted at predetermined intervals; Each time the common electrode potential is inverted, the lowest gray reference voltage and the highest gray reference voltage are set based on the contrast set value and the correction voltage set value. One of the voltages applied to the liquid crystal display pixel among the fluctuation center voltages of the respective gray level reference voltages each time the common electrode potential is inverted is set to be higher than the voltage corresponding to the correction voltage set value with respect to the other. A drive control method for a display drive device, characterized in that. The method of claim 12, The voltage corresponding to the correction voltage set value is, The voltage which is different from the value of the field-through voltage in the liquid crystal display pixel when one of the lowest gradation reference voltage or the highest gradation reference voltage is applied to the liquid crystal display pixel in the active matrix liquid crystal display panel. A drive control method for a display drive device, characterized in that a voltage value of a difference of a value of a field through voltage in the liquid crystal display pixel when it is applied. The method of claim 12, The setting method of the lowest gradation reference voltage and the highest gradation reference voltage based on the contrast setting value and the correction voltage setting value is Generates a plurality of gradation voltages, Whenever the potential of the common electrode is inverted from the gradation voltages of the plurality of steps, the maximum value of the first voltage and the number of steps corresponding to the first value based on the contrast setting value and the correction voltage setting value Selects and outputs a second voltage from the step corresponding to a value obtained by subtracting a second value based on the contrast set value and the correction voltage set value from; And setting the first voltage and the second voltage as the lowest gray reference voltage and the highest gray reference voltage each time the potential of the common electrode is inverted. The method of claim 14, The first and second values based on the contrast set value and the correction voltage set value are: Either the value by the contrast setting value or the value by subtracting the value by the correction voltage setting value from the value by the contrast setting value, And alternately setting each time the common electrode potential is inverted. The method of claim 14, The first and second values based on the contrast set value and the correction voltage set value are: A value obtained by subtracting the value of the correction voltage setting value from the maximum value of the number of steps of the gradation voltage and the value of the corresponding contrast setting value, A value according to the contrast setting value and a maximum value of the number of steps of the gradation voltage, which are set alternately each time the common electrode potential is inverted. The method of claim 14, The first and second values based on the contrast set value and the correction voltage set value are: A display in which the correspondence of the first and second values is reversed whenever the common electrode potential is reversed in polarity according to whether the active matrix liquid crystal display panel is normally white or normally black. Drive control method of drive system.